Alright, first step. Simply cut open the valve as shown with a saw. Use one with the thinnest blade you can find.
Remove the innards and look down into the casing. This is what you'll see:
Do you see that little ridge? That is what the piston seals against. It's completely safe to widen that hole but not go past the ridge. My actual valve opening wasn't concentric with the sealing ring, so I could just drill a bigger hole. I used a smallish drill bit on my dremel and carefully shaved away plastic until I hit the ridge. Finished hole:
Now just solvent weld everything back together and you have a much more efficient big salvo valve. Don't forget to put the piston back in before doing so!
Edited by TantumBull, 18 January 2010 - 07:22 PM.